The wet process ordinarily employed for toner particle production comprises dispersing or dissolving a pigment and a binder resin into an oily phase and mixing this oily phase with an aqueous phase to obtain fine toner particles. This process, however, has had problems, for example, that since the pigment has poor dispersibility into the oily phase or has a poor affinity of the organic solvent or binder resin with a pigment, colored toner particles having poor pigment dispersion are formed or part of the pigment is present outside the colored fine toner particles.
A method known as an expedient for overcoming these problems comprises treating the surface of pigment particles to improve the dispersibility of the pigment. For example, a technique of surface treatment is disclosed in JP-A-53-17737 (the term "JP-A" as used herein means an "unexamined published Japanese patent application.") and JP-A-58-7648 which comprises treating a pigment in an organic solvent with a silane coupling agent or a titanate coupling agent and then drying and heating the resulting pigment to chemically bond the silane or titanate coupling agent to the pigment surface.
However, the conventionally known technique for the surface treatment of a pigment has had a drawback that since the pigment treated in an organic solvent should be taken out of the organic solvent before being subjected to the subsequent processing, the pigment particles are apt to aggregate to form secondary particles, often resulting in a toner in which the pigment is poorly dispersed. Moreover, in the case of a metallic lake pigment, it is difficult even with the above conventional technique to inhibit the separation of pigment particles from colored fine toner particles. As a result, the toner thus obtained has impaired powder properties, e.g., poor electrostatic properties and reduced preservability, because of the pigment unevenly dispersed in the colored fine toner particles. The present invention has been attained under the circumstances described above.